Ethanol, chloride, calcium and growth cone dynamics in embryonic GABAergic interneurons

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Project Summary Fetal alcohol spectrum disorder (FASD) is one of the leading preventable neurodevelopmental disorders hallmarked by varying degrees of intellectual disability that includes cognitive, behavioral, sensory, and physical deficits. While the diagnosis and management of FASD takes place postnatally, the underlying pathoetiology is clearly embryonic but remains incompletely understood. In mice, prenatal ethanol exposure disrupts the intricate process of tangential migration of GABAergic cortical interneurons, and this has been postulated to contribute to long-term excitatory/inhibitory imbalance within the cortical circuits and impairments in executive function that lasts into adulthood. What cellular processes does ethanol affect to result in this aberrant migration? In this proposal, I will investigate the mechanisms underlying the migration of GABAergic interneurons and how this might be disrupted following ethanol exposure. My preliminary data to date suggest that the Na+-K+-2Cl- co-transporter isoform 1 (NKCC1), L-type voltage-gated calcium channels, and cytoskeletal dynamics may be involved in the action of ethanol on the migration of GABAergic cortical interneurons. Building on this, I propose two inter-related yet independent specific aims. Specific Aim 1 will employ a combination of perforated patch clamp recording and real-time imaging to test the hypothesis that ethanol interacts with NKCC1 to elevate intracellular chloride levels and enhance GABAA receptor-induced depolarization in embryonic GABAergic interneurons. Specific Aim 2 will use fluorescence calcium and actin-microtubule imaging to test the hypothesis that ethanol alters L-type calcium channel-dependent actin-microtubule dynamics to alter tangential migration of embryonic GABAergic cortical interneurons. Overall, through this F31 proposal, I seek intellectual, conceptual, and technical training that will be foundational for me to continue conducting research in the field of FASD, focusing on the cellular and subcellular mechanisms underlying ethanol’s effect on neuronal migration during brain development. The proposed work will set the groundwork for future investigations on how ethanol affects the subcellular signaling mechanisms that mobilize the growth cone as part of the migration process, and contribute critical mechanistic insights into how ethanol affects tangential migration and inform the design of therapeutic strategies to prevent or manage FASD.